What should be done first when performing a necropsy on a fish?

Starting the necropsy with the fish positioned right side down is the recommended first step. This positioning helps to ensure proper access to the anatomical structures and facilitates a thorough examination of the fish's body. By beginning with the right side down, the practitioner can systematically assess any potential lesions or abnormalities, as various organs and systems may be positioned in ways that are more easily viewed from this orientation.

Additionally, maintaining this positioning allows for a more controlled and methodical approach to the necropsy, decreasing the risk of contamination or misinterpretation of findings that may occur when handling the fish in an unorthodox manner. Following this method also aids in preserving the integrity of samples for further testing, as it allows for a clear view and minimizes damage to the fish's anatomy during the initial examination.

Consideration of the anatomical layout of the fish is vital, especially because certain organs may be oriented differently than in terrestrial animals, making the right side down position advantageous for maximizing the diagnostic yield of the necropsy.